Where do twins genetically come from?

This might not be the place to ask this, but where scientifically and genetically do twins come from? I've heard from the woman's side and the men's side so I'm very confused. My mom is adopted so I know nothing about her side. Im questioning because I have a really odd feeling there is 2 in me. The day my cycle was supposed to come the pink line was as bright as the constant line. Neon! My boobs have doubled in size and I've gained 10lbs. I'm also sicker than I ever imagined. I don't see it for a few more weeks, but wondering where they come from genetically to see if it's even a possibility?

IN MY OWN OPINION they come from the mothers side. When fraternal twins happen its multiple eggs and multiple sperm. Thats why it is so common in fertility treatments. When identical twins happen its because the fertilized egg splits into two. Therefore, the "babies" have identical dna. That's what I think i learned in anatomy but then again I'm not really sure if I was paying attention. Lol

Identical twins can happen to anyone. The single embroyp splits but was made an embroyo by one sperm so there DNA will be the same. Therefore that does not run in genetics.

However, fraternal twins is when you have two eggs release in a cycle and both become embroyos from different sperm. That can run in the family, but tends to skip a generation, and I would imgaine that that is via the mothers side (you) but who you get that from, either your mother or father's side I don't know. But fertility drugs can cause fraternal twins as well.